A polycarbonate-polyorganosiloxane polymer (hereinafter sometimes abbreviated as “PC-POS”) has been attracting attention because of its excellent properties such as high impact resistance, chemical resistance, and flame retardancy. Accordingly, the PC-POS has been expected to be widely utilized in various fields such as the field of electrical and electric equipment, and the field of automobiles. In particular, the utilization of the PC-POS in housings for a cellular phone, a mobile personal computer, a digital camera, a video camera, an electric tool, and the like, and in other commodities has been expanding.
In normal cases, a homopolycarbonate using 2,2-bis(4-hydroxyphenyl)propane [common name: bisphenol A] as a dihydric phenol as a raw material has been generally used as a typical polycarbonate. A polycarbonate-polyorganosiloxane copolymer using a polyorganosiloxane as a copolymerizable monomer has been known for improving the physical properties of the homopolycarbonate such as flame retardancy and impact resistance (see Patent Documents 1 to 3).
When the impact resistance of the polycarbonate-polyorganosiloxane copolymer, in particular, its impact resistance under low temperature is improved, as disclosed in Patent Document 3, a method involving using a polyorganosiloxane having a long chain length has been known. However, the method has involved a problem in that the transparency of the copolymer reduces.
On the other hand, a method involving using a polyorganosiloxane having a relatively short chain length has been known for improving the transparency of the polycarbonate-polyorganosiloxane copolymer (see Patent Documents 4 and 5). However, the method has involved a problem in that the impact resistance of the copolymer reduces.
In addition, the following attempt has been made in Patent Document 6. Two kinds of polycarbonate-polyorganosiloxane copolymers having different light transmittances are blended to improve transparency while maintaining excellent impact resistance. However, the transparency cannot be said to be sufficient. As described above, it has been difficult to achieve compatibility between excellent transparency and excellent impact resistance, in particular, impact resistance under low temperature in a conventional polycarbonate-polyorganosiloxane copolymer.